Pfizer and Lilly restart tanezumab pain trials

The FDA has lifted a block on clinical trials of Eli Lilly and Pfizer's novel painkiller tanezumab, clearing the way for phase III trials to resume.

Tanezumab blocks nerve growth factor (NGF) and if approved would represent the first entirely new class of pain drugs in more than a decade.

The US regulator has placed two separate clinical holds on the project in the last five years. In 2010 the FDA introduced a block on concerns about a rare side effect called osteonecrosis - which was subsequently relaxed - only for another to be imposed in 2012 after the entire class of NGF inhibitors came under scrutiny for peripheral nervous system side effects.

The FDA has now removed the clinical hold after a review of "nonclinical data characterising the sympathetic nervous system response to tanezumab" which was submitted to the agency last month, according to a joint statement from Pfizer and Lilly.

They added that prior clinical studies involving more than 11,000 patients have shown that tanezumab is associated with clinically meaningful efficacy compared to placebo and other commonly used pain medicines.

Lilly licensed co-development rights to tanezumab from Pfizer in 2013, banking on the rehabilitation of the NGF inhibitor class, which at the time also included clinical candidates such as Johnson & Johnson's fulranumab and Regeneron/Sanofi's fasinumab, among others.

J&J and Regeneron have previously indicated they intend to move their antibodies into pivotal trials once the latest clinical hold was lifted, and both companies have submitted supportive data to the FDA to achieve that.

The Lilly agreement was worth up to $1.8bn to Pfizer - including as well as $350m in regulatory milestones and $1.23b in sales milestones - reflecting the optimism at the time that HGF inhibitors could eventually become a $10bn-plus product category with applications across many different chronic pain indications.

Pfizer is in line to receive an upfront payment of $200m from Lilly thanks to the removal of the clinical hold.

Sales expectations for the class have been scaled back in recent years, however, with analysts at Cowen & Co predicting sales of $100m for tanezumab in 2020, with additional upside if it can secure approval in multiple chronic pain indications.